British conservationists say two critically endangered eastern black rhinos bred in captivity in England have given birth in Africa.

The Aspinall Foundation said Sunday the two females bred at its wildlife park in southern England and released in Tanzania have given birth after mating there with a male who had also been bred in captivity.

The two females named Grumeti and Zawadi were given a sendoff by Prince William when they departed for Tanzania in 2012. William has been active in recent years in trying to protect wildlife.

The foundation says each female has given birth in recent weeks to healthy babies.

Foundation chairman Damian Aspinall says the births represent a "remarkable and vital" breakthrough in the bid to protect this endangered species. He says strong habitat protection is also needed.